APPLICANT'S ABSTRACT: The overall aim of this study is to test the "matching hypothesis" that alcohol treatment effectiveness can be increased by assigning clients with certain characteristics to particular treatments. The present application proposes to continue work initiated and conducted over the past five years. The specific aims of the study are: to test primary and secondary a priori matching hypotheses over the course of 15 months of follow-up; to conduct psychometric and other analyses of patient, treatment process, and outcome variables to test these matching hypotheses; to examine alternative analytic strategies and variables for testing matching; and to determine the extent to which matching effects persist over a three year period following treatment completion. Data sets collected form the Project MATCH outpatient (N=954) and aftercare (N=774) arm of the trial will be analyzed top achieve these aims. Clients were randomly assigned to one of three treatments, Twelve Step, Cognitive Behavioral, or Motivational Enhancement. They were assessed prior to treatment on baseline and matching variables and followed, at 3 month intervals, for 15 months from treatment assignment to measure their alcohol consumption and other dimensions of outcome. To test longer term matching effects clients in the outpatient arm of the study will be contacted and assessed at 39 months after treatment initiation. It is anticipated that study results will impact on alcohol treatment research and delivery for the next decade. The Project MATCH Steering Committee, following discussion with NIAAA Staff, has chosen to submit a generic proposal across each of the CRUs, reflecting the common protocol and cooperative process that has guided the project across its first five years of operation. However, each CRU has provided site-specific information in the budget, budget justification, listing of key personnel, consultation/consortium agreements, and human subjects sections of their respective proposals.